EAs are inherently dangerous. There are a lot of things an EA will do in live mode that are bad and it may not do them in a back test. You need to know it will not re open a position that just got stopped out over and over again. I have seen positions opened and then closed hundreds of times in one minute. That is a lot of spreads and slippage to cover. You need to consider if the EA will have a position open over the weekend or when the market is closed or when the traders you are relying on to make a signal profitable are on holiday.

Manual trading has pitfalls. You need to NEVER vary the size of your trade by your feelings about a particular set up and ALWAYS trade the size you back tested for. etc.

An EA that can be trusted an easily notice trade setups and act on them 1000 times faster than following an indicator can.

The greatest benefit of trading with profitable EAs is that you can live your life in the world and not spend all day every day sitting at a screen being bored. If you can trade profitably at all you can trade more profitably with (Well designed and written) EAs.

A lot depends if you are a programmer, a trader, or an investor. There are all types here and all combinations.

Obviously you are new so you should try out DEMO accounts first until you know what your goals are and how you are going to get there. Don't start by spending a lot of money or trying to reinvent the wheel. There are plenty of free EAs and indicators to try out your skills and develop some experience. Don't be in too big of a rush because that is how new traders are eaten alive.

In my opinion, a signal is more reliable than a robot, but you also need to consider the drawdown because a signal with a huge drawdown could clean out your account, well, that depends on several factors.